Electromechanical door holders and automatic door operators are two types of devices that provide automatic functions with respect to doors. Electromechanical door holders generally include a door closer and apparatus that arrests the operation of the door closer. Electromechanical door holders may be attached to the structure adjacent to a door, such as a door frame or wall, and a pivotable arm extends from the door operator to the door, or alternatively, the electromechanical door holder may be mounted to the door, and the pivotable arm may extend to the adjacent structure. The door closer is intended to provide a smooth, controlled closing action to the door after the door has been opened and released.
Many conventional door closers are mechanically actuated and have a piston and a plurality of springs and valved ports. The piston moves through a reservoir filled with a hydraulic fluid, such as oil. The piston is coupled to the door closer's arm through a rack and pinion such that, as the door is opened, the piston is moved in one direction and, as the door is closed, the piston is moved in the opposite direction. As the piston moves, it displaces hydraulic fluid, which may be forced through various ports. The force exerted by the door closer depends on loading of a compression spring and the speed of the action depends on the open or closed status of the ports. The ports are adjustable (open or closed) via needle valves that control flow of hydraulic fluid between chambers, and the compression spring setting may or may not be adjustable based on the construction of the door closer. The valves may be operated with solenoids connected to a power supply. Energizing a solenoid may close a valve, prevent flow of hydraulic fluid, and thereby provide a hold-open feature to the door closer, making an electromechanical door holder.
With respect to door operators, the purpose of a door operator is to open and close a door. In general, a door operator may be mounted similarly to an electromechanical door holder. Automatic, hinged doors with door operators generally include motorized door openers and door closers that may be powered or spring assisted. The door may open manually or automatically upon actuation of a switch often placed on a wall proximate to the door. When automatic operation is initiated, the door commonly proceeds through a sequence that includes starting the motor, the motor driving the door to an open position, the door being held open for a set period, and then the motor turning off or reversing direction to allow the door closer to close the door.
A variety of automatic door operators is known. A typical door operator includes an electric motor and a linkage assembly for operatively coupling the drive shaft of the motor to a door so that the door will be opened and closed when the drive shaft rotates. Activation of the door operator is initiated by means of an electric signal generated in a variety of ways such as, for example, a pressure switch, an ultrasonic or photoelectric presence sensor, motion sensors, radio transmitters, wall switches, and the like. The door may then be closed under power or with a door closer, as used in an electromechanical door holder.
The automatic, predetermined timing of closing of an automatic door with either a door operator or a door holder creates the opportunity for the door to close on a person who or an object that does not or cannot pass through the doorway in sufficient time to avoid the closing door.